Where it Snows

This graphic shows the average annual maximum and minimum snow cover in the Northern Hemisphere. Grey indicates snow cover and white shows sea ice cover, which in the winter would also be snow covered.
—Credit: NSIDC

Snow requires two specific weather conditions: low temperatures and moisture in the atmosphere. In warm, humid places, such as Florida, there is significant moisture in the air, but temperatures are rarely low enough to produce snow. And while many deserts get quite cold in the winter, there is often not enough moisture in the atmosphere to produce snow. Even Antarctica, the coldest and iciest continent, contains a region called the Dry Valleys, where it is extremely cold, but so dry that snow never falls.

Snow is most common in high altitudes and high latitudes, particularly among the mountainous regions of the Northern and Southern Hemispheres. Annually, snow covers as much as 46 million square kilometers (about 17.8 million square miles), particularly over North America, Greenland, Europe, and Russia. Nearly every location in the United States has seen snowfall. Even portions of Florida have received a few snow flurries.

Snow also falls in the Southern Hemisphere during the austral winter, primarily in Antarctica and in the high mountains of New Zealand and South America.

Local and regional snowfall patterns

In the United States, lake effect snow frequently occurs around the Great Lakes, generating heavy snowfall downwind in â€œsnowbeltâ€ states, such as Michigan and New York. (Larger image not available)
—Credit: Phizzy, Wikimedia Commons

Although snow is commonly associated with mountains, other geographical features can promote the formation of snow. Large lakes, for instance, can produce locally heavy snow, often called lake effect snow. As cold, dry air passes over the lakes, it picks up moisture and heat from the relatively warm water. The heated air rises, cools off, and the moisture condenses to form clouds. If these clouds contain enough moisture, they will produce snow once they come into contact with land. Lake effect snow is common along the southern and eastern edges of the Great Lakes in the United States and near the Great Salt Lake in Utah, as well as around some of the large lakes in Canada and Europe. The United Kingdom, Japan, and Korea also experience similar phenomena, but the snow-producing moisture comes from the surrounding oceans instead of lakes.

Winter weather can sometimes create turbulent conditions as the air heats and rises or cools and descends. A rare and strange byproduct of this turbulence is thunder snow, which is a snowstorm with thunder and lightning.

Local weather patterns can also produce snow. For instance, the northeastern coast of the United States is often battered by storms called Nor'easters, which produces heavy snow, rain, and waves that crash onto the beaches.